Linux Kernel CXL Driver cxl_region_attach_auto targets/nr_targets null pointer dereference

Summaryinfo

A vulnerability categorized as critical has been discovered in Linux Kernel. Impacted is the function cxl_region_attach_auto of the component CXL Driver. Such manipulation of the argument targets/nr_targets leads to null pointer dereference. This vulnerability is referenced as CVE-2026-74274. The attack can only be performed from a local environment. No exploit is available.

Detailsinfo

A vulnerability was found in Linux Kernel (affected version unknown). It has been rated as critical. Affected by this issue is the function cxl_region_attach_auto of the component CXL Driver. The manipulation of the argument targets/nr_targets with an unknown input leads to a null pointer dereference vulnerability. Using CWE to declare the problem leads to CWE-476. A NULL pointer dereference occurs when the application dereferences a pointer that it expects to be valid, but is NULL, typically causing a crash or exit. Impacted is confidentiality, integrity, and availability. CVE summarizes:

In the Linux kernel, the following vulnerability has been resolved: cxl/region: Fill first free targets[] slot during auto-discovery Any invalid endpoint decoder pointer in the target array of an active region is not allowed by cxl driver. This means cxl driver always assumes the first p->nr_targets entries of the target array in an auto-assembly region are valid. However, there are scenarios that could leave NULL endpoint decoder pointer holes in the target array. 1. When cxl_cancel_auto_attach() removes an endpoint decoder from a target array, the target slot is set to NULL. If the removed endpoint decoder is not the last element in the target array, the target array will contain a NULL hole. 2. When a auto-assembly region removes an assigned endpoint decoder, if the removed endpoint decoder is not the last element in the target array, always remains a NULL hole in the target array. When a NULL pointer hole exists in a region's target array, it introduces two potential problems: 1. Access an endpoint decoder via a NULL pointer. it always trigger calltrace like that. Oops: general protection fault, probably for non-canonical address 0xdffffc0000000008: 0000 [#1] SMP KASAN PTI RIP: 0010:cxl_calc_interleave_pos+0x26/0x810 [cxl_core] Call Trace: <TASK> cxl_region_attach+0xc50/0x2140 [cxl_core] cxl_add_to_region+0x321/0x2330 [cxl_core] discover_region+0x92/0x150 [cxl_port] device_for_each_child+0xf3/0x170 cxl_port_probe+0x150/0x200 [cxl_port] cxl_bus_probe+0x4f/0xa0 [cxl_core] really_probe+0x1c8/0x960 __driver_probe_device+0x323/0x450 driver_probe_device+0x45/0x120 __device_attach_driver+0x15d/0x280 bus_for_each_drv+0x10f/0x190 2. Not having enough valid endpoint decoders attached to an auto-assembly region. if an auto-assembly region is created with lock flag or assigned endpoint decoder with lock flag, which means assigned endpoint decoder will not be reset during detaching, they could re-attach to the auto-assembly region again. But cxl region driver relies on p->nr_targets to verify whether the required number of endpoint decoders has been attached, and NULL endpoint decoder pointers are still counted in that case. To fix above issues, adjust cxl_region_attach_auto() logic to find the first free target slot for endpoint decoder attachment, this ensures NULL holes in the target array are filled, rather than adding new endpoint decoders at the tail of the target array.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-74274 since 08/15/2026. The exploitation is known to be easy. Local access is required to approach this attack. The exploitation requires an enhanced level of successful authentication. Successful exploitation requires user interaction by the victim. Technical details are known, but there is no available exploit.

Applying the patch 6fde3fcdfec438ba0df26e25a8ac7c3707211799/aa8a76711c15041ec1e42c3a74c15c2df0bd31f6 is able to eliminate this problem.

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Productinfo

Type

• Operating System

Vendor

• Linux

Name

• Kernel

License

• open-source

Website

• Vendor: https://www.kernel.org/

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